MySQL database Triggers

MySQL database Triggers

1. Trigger with only one row of statements executed

Trigger triggers are events that trigger certain operations, such as insert, delete, and update.

 

For example:

create trigger t_user_trig before inserton t_user for each rowinsert into trigger_time values(now());

Create a trigger named t_user_trig to insert the current time to the trigger_time table when inserting the t_user table.

Test:

insert into t_user values(2,'wang',0,'abcdef',now(),'a');select * from trigger_time;

 

2. Trigger with multi-row statement execution

 

 

Example:

delimiter &&create trigger t_user_trig_del after deleteon t_user for each rowbegininsert into trigger_time values('2000-01-01 10:10:00');insert into trigger_time values('2001-01-01 11:11:00');end&&delimiter;

Create a trigger named t_user_trig_del. After deleting the t_user record in the table, two insert statements are executed.

Select * from trigger_time;

3. View triggers

 

Select * from information_schema.triggers where trigger_name = 't_user_trig ';

 

4. delete a trigger